Noodling for Mollusks: Practicing Field Sampling in the Science Classroom

Article excerpt

Anyone who has ever noodled for organisms knows the thrill of the catch. Students may have heard of noodling catfish, a hazardous pastime in which a person wiggles a finger in hopes of catching a fish. Others may have never heard of this process of searching for a given organism using your sense of touch but not your sense of sight.

Mollusks, such as mussels and snails, are a great group to noodle because they are prevalent in banks and bottoms of river basins and in sandy beach habitats. Furthermore, their shells are easy to come by and safe to handle. There are six classes within the phylum Mollusca. In the activities described in this article, we focus on the gastropod (e.g., snails) and bivalve (e.g., mussels) classes. Bivalves serve as good water-quality indicators due to their intolerance of wastewater treatment effluent and other anthropogenic (human-introduced) pollution sources.

Mollusks play important roles within their ecosystems, but degradation of natural habitat, decreasing water quality, and increasing artificial structures contribute to the decreasing prevalence of freshwater species. In the two activities we describe in this article, designed for middle or high school life science or biology classes, students noodle bivalves and gastropods from a covered container, determining organism density as number per square meter and catch per unit effort. Students analyze their results and learn about using species as indicators of reduced habitat quality. (Safety note: Noodling for fish or mollusks in the wild is dangerous and should not be attempted by students.)

Understanding the mollusk

Gastropods move slowly, and mussels are nearly, if not completely, sessile (immobile)--making these creatures easy to sample. Malacologists (zoologists who study mollusks) noodle to randomly sample the aquatic environment and assess the abundance or density of mollusks. These researchers have to be aware of the sampling environment to understand their target organism because some species (e.g., snails from the genus Conus) can be venomous. Mala-cologists also investigate noodling sites to draw statistical conclusions about trends.

Mollusks serve roles (niches) in their ecosystems as scavengers and water purifiers and also serve as food sources for organisms in many freshwater and marine ecosystems. But as waterways become more polluted, many mollusks are disappearing. North America's freshwater mussel species (Bi-valvia: Unionidae) were once a major part of the southeastern aquatic faunal diversity (Neves 1997). Now, over 75% of them are recognized as threatened or endangered. This decline is due to habitat loss and degradation, sedimentation, increases in nutrients, contaminants, and dam creation (Schilling and Williams 2002; Neves 1997). Some freshwater mussel species live in blackwater rivers that contain high concentrations of tannic acid from adjacent riverine swamp areas.

Noodling site construction

The two noodling activities described in this article are based upon a mollusk inventory that the first author conducted in the Canoochee River, Georgia (Figure 1; Sukkestad et al. 2005). Sampling was conducted at 235 locations, each with multiple replicate sites, and higher densities were found in the upper coastal plain of Georgia (68.42 mussels [h.sup.-1]) than the lower coastal plain (52.4 mussels [h.sup.-1]). (Mussel density is measured as catch per unit effort (CPUE = number per hour = no. [h.sup.-1]) The population was estimated based on the values obtained across all these sites. Having replicate samples at multiple sites is important to draw sound conclusions, which is why we use multiple bins when we recreate this inventory in the classroom. This helps to provide a statistical foundation for the classroom activity described here.

Before the classroom portion of this activity, teachers must first construct the noodling bins (Figure 2) using the following materials:

* one large 15 x 34 x 5. …